Piston Pump for Thick Substances

ABSTRACT

The invention relates to a piston pump for thick matter, in particular for high-solids sewage sludge, coal sludge and concrete. The piston pump has at least one delivery cylinder ( 16 ) which contains a motor-driven or hydraulically driven delivery piston ( 20 ) and which has an orifice ( 12 ) which communicates alternately with the interior of a material feed container ( 10 ) and with a pressure delivery line ( 30 ) in a slide-controlled manner in accordance with the movement of the delivery piston ( 20 ). In order to significantly increase the degree of filling of the at least one delivery cylinder ( 16 ), an annular nozzle ( 32 ) opening into the delivery cylinder ( 16 ) in the region of the orifice ( 12 ) is provided, and this annular nozzle ( 32 ) is connected to an external pressure line ( 34 ) to which a lubricant can be admitted.

The invention relates to a piston pump for thick substances, having atleast one feed cylinder containing a motor-driven or hydraulicallydriven feed piston, which cylinder has an orifice opening thatalternately communicates with the interior of a material applicationcontainer and with a pressure feed line, as determined by the movementof the feed piston, controlled by a slide.

Piston pumps of this type are used to convey mixtures of solids andliquids that have a high proportion of solids, such as, for example,sewage treatment sludge, coal slurry, biomass, or concrete. Such thicksubstances have a high internal friction, so that the degree of fillingof the feed cylinders frequently leaves something to be desired duringthe suction process. On the other hand, it is known, in the case ofpiston pumps of this type (EP-B-633863), to introduce a lubricantbetween the strand of thick substance and the wall of the pressure feedline, in order to reduce the wall friction, at the entrance of thepressure feed line. This is usually done continuously, and in a meteredamount proportional to the feed stream, with the result that a borderlayer forms between the inner wall of the pipe and the thick-substancestrand, by means of which the feed pressure can be reduced. Since thelubricant layer gradually disappears along the feed distance, additionallubricant has to be injected into the pressure feed line at certainintervals. In order to increase the degree of filling of the feedcylinder, a pre-pressing device is usually provided in the region of thematerial application container, with which device the filling pressurecan be raised by at least 1 bar. In many cases, however, this is notsufficient.

Proceeding from this, the invention is based on the task of improvingthe known piston pump for thick substances, to the effect that thedegree of filling in the feed cylinder can be significantly increased,even at high proportions of solids in the thick-substance material.

To accomplish this task, the combination of characteristics indicated inclaim 1 is proposed. Advantageous embodiments and further developmentsof the invention are evident from the dependent claims.

The solution according to the invention is primarily based on the ideathat a ring nozzle that opens into the feed cylinder is disposed in theregion of the orifice opening, which nozzle is connected with anexternal pressure line, whereby the pressure line can have a lubricantapplied to it by way of a high-pressure pump. It is advantageous if thepressure line is connected with a ring channel that opens into the ringnozzle, by way of a bore disposed in the orifice region of the feedcylinder.

A preferred design embodiment of the invention provides that the feedcylinder carries an outer ring that has at least one bore connected withthe pressure line on the outside, having a ring channel that leads tothe ring nozzle, whereby the ring channel is delimited on the inside byan outer surface of the feed cylinder, or of an inner ring that followsit axially, and on the outside by an inner surface of the outer ring. Itis practical if the aforementioned inner ring engages into a recess ofthe outer ring that is open towards the inside, and delimits the ringchannel and the ring nozzle together with this ring. In this connection,it is advantageous if the inner ring is braced between two ring surfacesof the feed cylinder and of the outer ring body that face one another,with a rear, radially projecting collar.

In order to guarantee uniform distribution of the thick substances overthe circumference, it is practical if the ring channel has at least onering-shaped widening in cross-section. It is advantageous if tworing-shaped widenings in cross-section are provided, disposed at adistance from one another.

According to a preferred embodiment of the invention, a control devicethat responds to the position and/or the stroke direction of the feedpiston in the feed cylinder, and a control valve that responds to anoutput signal of the control device and is disposed in the pressureline, which opens during the suction stroke of the feed piston andcloses before its pressure stroke, are provided. In this connection, itis practical if the control valve is configured as a directional valvethat can be controlled by way of the feed piston, preferablymagnetically.

A preferred embodiment of the invention provides that two feedcylinders, which each have a ring nozzle in their orifice region, areprovided, whose ring nozzles can have lubricant applied to them, by wayof the control valve, during every suction stroke of the feed piston,which is controlled with opposite cycles.

The invention furthermore relates to a method for operation of a pistonpump for thick substances, in which thick-substance material isalternately drawn into a feed cylinder that is open on one side, duringa suction stroke, and pressed out of the feed cylinder into a pressurefeed line during a subsequent pressure stroke. In order to significantlyincrease the degree of filling of the feed cylinder, it is proposed,according to the invention, that a lubricant is injected into the feedcylinder during every suction stroke. In this connection, it isadvantageous if the lubricant is injected into the separation regionbetween thick-substance material and feed cylinder inner surface,specifically over its entire circumference. In order to preventunintentional emptying of the incoming lines for the lubricant, it ispractical if the lubricant injection is interrupted during the pressurestroke. The lubricant is injected at a higher pressure than that of thethick substance disposed in the feed cylinder. It is practical if theinjection pressure is more than 50, preferably about 100 bar, while itis practical if the pre-pressing pressure in the thick-substancematerial during the suction stroke is approximately 2 bar.

A preferred embodiment of the invention provides that in the case of atwo-cylinder piston pump, the pistons in a first and a second feedcylinder are controlled in opposite cycles, performing a suction strokeand a pressure stroke, whereby a lubricant is injected into the feedcylinders during every suction stroke, and the lubricant injection isinterrupted during the pressure stroke, in each instance.

Using the measures according to the invention, a significant improvementin the degree of filling in the feed cylinder is achieved, particularlyin the case of thick substances having a high proportion of solids.Furthermore, the lubricant layer that forms in the feed cylinder isentrained into the pressure feed line, so that in a first line sectionthat follows the thick-substance pump, an additional lubricant injectionis no longer necessary. Only in the case of long pressure feed lineshaving a length of more than 50 to 100 m can additional lubricant beinjected into the pressure feed line, at a distance from thethick-substance pump. While the lubricant is injected into the feedcylinder only during the suction stroke, lubricant injection into thepressure feed line should take place continuously.

In the following, the invention will be explained in greater detailusing an exemplary embodiment shown schematically in the drawing. Thisshows:

FIG. 1 a top view of a two-cylinder piston pump for thick substances,for connection to a feed line;

FIG. 2 a and b a top view and a sectional representation of thetwo-cylinder piston pump according to FIG. 1, in an enlargedrepresentation, without the material application container;

FIG. 3 an enlarged detail of the sectional representation according toFIG. 2 b;

FIG. 4 a section through the orifice region of one of the feedcylinders, in a representation that is enlarged as compared with FIG. 3.

The two-cylinder thick-substance pump shown schematically in FIG. 1 isintended to convey thick substances that are rich in solids, such aspartially dewatered sewage treatment sludge, coal dust sludge, orconcrete, for example.

The piston pump consists essentially of a material application container10; two feed cylinders 16 connected to the material applicationcontainer 10 by way of their face-side orifice openings 12, by way ofwall openings 14; two feed pistons 20 that can be driven in the feedcylinders 16 in opposite cycles, by way of hydraulic drive cylinders 18;and a water box 22 disposed between the drive cylinders 18 and the feedcylinders 16. A pipe slide 21 is disposed within the materialapplication container 10; it can be alternately connected to the orificeopening 12 of the feed cylinder, whose piston is performing a pressurestroke, with its entry opening 26, and releases the orifice opening 12of the other feed cylinder, whose piston is performing a suction stroke,and its exit opening 28 is connected with a pressure feed line, notshown, by way of a pressure connector 30 disposed on the materialapplication container 10. In the case of the exemplary embodiment shownin FIG. 1, the pipe slide 24 has a pivot pipe curved in S shape, whichcan pivot within the material application container 10. Accordingly,thick-substance material gets from the interior of the materialapplication container 10, if necessary with the exertion of apre-pressing pressure, into the related feed cylinder 16, by way of theopen orifice opening 12, during every suction stroke, while thethick-substance material situated in the other feed cylinder 16 ispressed into the subsequent pressure feed pipe, by means of the feedpiston 20, performing a pressure stroke, by way of the pivot pipe of thepipe slide 24 and the pressure connector 30.

A particular feature of the invention consists in the fact that a ringnozzle 32 is disposed in the region of the orifice opening 12, whichnozzle can have a lubricant at a pressure of approximately 50 to 100 barapplied to it, by way of pressure pipes 34, bores 36, and a ring channel38. To form the ring channel 38 and the ring nozzle 30, an inner pipe 40axially follows the feed cylinder 16 in the region of the orificeopening 12, which pipe is covered by an outer pipe 42 screwed onto thefeed cylinder 16. For this purpose, the inner ring 40 has a radiallyprojecting collar 44, which is braced between a ring surface 46 of theouter pipe 42 and the face-side ring surface 48 of the feed cylinder 16,in such a manner that the ring nozzle 32 and the ring channel 38 betweeninner pipe and outer pipe remain open. The bores 36 for the lubricantsupply are disposed in the outer pipe 42. The inner pipe 40 has two ringgrooves on its inner surface that delimits the ring channel 38, whichform a cross-section widening 50 and ensure uniform distribution of thelubricant that exits from the ring nozzle 32, over the circumference.

For the lubricant supply to the individual feed cylinders 16, anexternal control device, not shown, is controlled in such a manner thatlubricant is injected into the feed cylinder only during the suctionstroke. There, the lubricant gets into the separation region betweenthick-substance material and feed cylinder inner surface, so that thedegree of filling is improved because of the reduced slide friction.Experiments have shown that using the measures according to theinvention, it is possible to achieve an improvement in the degree offilling of at least 25%, in the case of sewage treatment sludges thatare rich in solids. During the subsequent pressure stroke, the lubricantgets into the pressure line, together with the thick-substance material,and also reduces the slide friction there, and thus reduces the feedpressure required for the material transport. During the pressurestroke, the lubricant injection is interrupted, in each instance. Inthis way, the risk of emptying the lubricant line because of thethick-substance material that is flowing past it is avoided.

In summary, the following should be stated: The invention relates to apiston pump for thick substances, particularly for sewage treatmentsludge, coal slurries, and concrete, which are rich in solids. Thepiston pump has at least one feed cylinder 16 containing a motor-drivenor hydraulically driven feed piston 20, which cylinder has an orificeopening 12 that alternately communicates with the interior of a materialapplication container 10 and with a pressure feed line 30, as determinedby the movement of the feed piston 20, controlled by a slide. In orderto significantly increase the degree of filling of the at least one feedcylinder 16, a ring nozzle 32 that opens into the feed cylinder 16 isprovided in the region of the orifice opening 12, which nozzle isconnected with an external pressure line 34 to which lubricant can beapplied.

1-18. (canceled)
 19. Piston pump for thick substances, having at leastone feed cylinder (16) containing a motor-driven or hydraulically drivenfeed piston (20), which cylinder has an orifice opening (12) thatalternately communicates with the interior of a material applicationcontainer (10) and with a pressure feed line (pressure connector 30), asdetermined by the movement of the feed piston (20), controlled by aslide, wherein a ring nozzle (32) that opens into the feed cylinder (16)is disposed in the region of the orifice opening (12), which nozzle isconnected with at least one external pressure line (34), that thepressure line (34) can have a lubricant applied to it by way of ahigh-pressure pump, and is connected with a ring channel (38) that opensinto the ring nozzle (32), and wherein the feed cylinder (16) carries anouter ring body (42), which has at least one bore (36) connected withthe pressure line (34) on the outside, having a ring channel (38) thatleads to the ring nozzle (32).
 20. Piston pump according to claim 19,wherein the ring channel (38) is delimited on the inside by an outersurface of the feed cylinder, or of an inner pipe (40) that follows itaxially, and on the outside by an inner surface of the outer ring body(42).
 21. Piston pump according to claim 19, wherein an inner pipe (40)follows the feed cylinder (16), on the face side, which pipe engagesinto a recess of the outer ring body (42) that is open towards theinside, and delimits the ring channel (38) and the ring nozzle (32)together with this ring body.
 22. Piston pump according to claim 19,wherein the ring channel (38) has at least one ring-shaped cross-sectionwidening (50).
 23. Piston pump according to claim 22, wherein the ringchannel (38) has two ring-shaped cross-section widenings (50), spaced ata distance from one another.
 24. Piston pump according to claim 19,further comprising a control device that responds to the position and/orthe stroke direction of the feed piston (20) in the feed cylinder (16),and a control valve that responds to an output signal of the controldevice and is disposed in the pressure line (34).
 25. Piston pumpaccording to claim 24, wherein the control valve disposed in thepressure line (34) opens during the suction stroke of the feed piston(20) and closes before its pressure stroke.
 26. Piston pump according toclaim 24, wherein the control valve is configured as a directional valvethat can be controlled by way of the feed piston (20), preferablymagnetically.
 27. Piston pump according to claim 19, wherein two feedcylinders (16), which each have a ring nozzle (32) in their orificeregion (12), are provided, whose ring nozzles (32) can have lubricantapplied to them, by way of the control valve, during every suctionstroke of the feed piston (20), which can be controlled in oppositecycles.
 28. Piston pump according to claim 19, wherein the inner pipe(40) is braced between two ring surfaces (46, 48) of the feed cylinder(16) and of the outer ring body (42) that face one another, with a rear,radially projecting collar (44).
 29. Method for operation of a pistonpump for thick substances, in which thick-substance material isalternately drawn into a feed cylinder (16) that is open on one side,during a suction stroke, and pressed out of the feed cylinder into apressure feed line during a subsequent pressure stroke, whereinlubricant is injected into the feed cylinder (16) during every suctionstroke, whereby the lubricant is injected over the entire circumferenceof the feed cylinder inner surface into the separation region betweenthick-substance material and feed cylinder inner surface.
 30. Methodaccording to claim 29, wherein the lubricant injection is interruptedduring the pressure stroke.